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Gulf of Mexico Oil Spill Questions and Answers: New Testing Method for Chemical Analysis of Seafood Samples for Presence of Oil Residues

Assessing the Impact of the 2010 Gulf Oil Spill Main Page

Q: What is FDA doing to speed the chemical testing of Gulf seafood for the presence of oil residues?

A: The current test, which is the reference test and was developed by NOAA for research purposes and confirmatory testing, takes 5-7 days. Given the urgent need to reopen Gulf of Mexico waters as soon as both the water and seafood are safe, FDA worked aggressively with our scientific partners to find an alternative test that is a reliable, accurate, and efficient way to test Gulf seafood for harmful levels of chemicals known as polycyclic aromatic hydrocarbons (PAHs).

This new testing method will reduce the analysis time from more than a week down to about 48 hours. If PAHs are detected or if results are inconclusive, samples will undergo testing using the confirmatory test. However, if no PAHs are detected the results can be used immediately to make decisions regarding reopening of waters.

Q: Are you sure this new chemical analysis will work? Is it effective at identifying oil contamination?

A: FDA scientists reviewed a previously developed method to determine if it would meet our standards for chemical testing. The FDA then refined the method so it was appropriate for testing of seafood from the Gulf. The test was evaluated and validated by FDA staff and other labs by testing samples spiked with known quantities of PAHs that were at or below the level of public health concern. Conducting a variety of sample tests helps us determine whether this analysis will be accurate.

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Q: How does this test work?

A: The test uses acetonitrile, a chemical solvent, to remove the chemical compounds that are of concern to public health, from the seafood. This is one of the steps that reduces the testing time needed in the FDA method. These chemicals of concern are then separated from one another using high performance liquid chromatography and detected by fluorescence spectroscopy. These chemical compounds of concern to public health can be detected by fluorescence spectroscopy at extremely low concentrations (parts per billion). Based on this test we can confirm that the level of these chemicals in the Gulf seafood are below a level that would cause public health concern.

Q: How does this new testing method compare to what you used in the past?

A: The new testing method is quicker and it is also effective at finding that there is no polycyclic aromatic hydrocarbons (PAH) contamination approaching the established levels of concern. The new method will be used for all reopening samples. The new testing method may be more sensitive to potential PAH contaminants. Thus, positive (or even indeterminate) findings of contamination will undergo testing using the original method to fully confirm is the level of PAH contamination.

Q: Will all FDA labs be using this method?

A: Not all labs will use this method. Some will continue to use the reference method, which does take longer, but is more effective for confirming positive findings or making decisions about inconclusive findings.

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FDA’s forensic chemistry lab in Cincinnati, OH, along with laboratories from the states of Minnesota and Connecticut are prepared right now to receive and analyze seafood samples using the new method. Labs in the Gulf region are being used for certain testing, but the labs mentioned above are those equipped to handle this specific chemical testing. We are in the process of expanding our sample analysis capability by extending the method additional FDA labs and state labs participating in our cooperative agreement with the Food Emergency Response Network.

Q: Once a state sends seafood samples to one of the labs using the new testing method, what happens?

A: Under the agreed-upon reopening protocol, seafood samples will be received at these labs after sensory testing (smelling and tasting) by expert panels at NOAA’s seafood testing laboratory in Pascagoula, MS. Once the samples pass the sensory test these are sent for chemical testing. Using the new method we anticipate having test results for the samples approximately 48 hours after receipt of the samples.

If the results are negative, FDA will communicate its findings to the state that submitted the sample to inform their decision on re-opening.

If the results are positive or inconclusive, the sample will be tested again using the previous method with results expected 5-7 days later.

Q: How many seafood samples can you test each day?

A: Each lab can test approximately 20 samples every 24 hours using the new method.

Q: What kind of seafood can you test using this new method?

A: This new method can be used to test seafood commonly harvested from the Gulf of Mexico, including finfish, oysters, shrimp, and crab, for the presence of PAHs due to oil contamination.

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